Calibration devices, such as liquid level devices, also known as "sight gauges" or "sight glasses," have been used in the past to calibrate liquid in a particular device being calibrated. Such calibration devices typically include a window interposed between a cover clamped to a chamber. The window allows visual inspection of the level of liquid in the chamber. The gauge can be fastened to a wall of the chamber or connected in parallel piping to a pipe or conduit. Graduations on the outer surface of the liquid level gauge around the window indicate the level of liquid within the liquid level device, and hence, within the device being calibrated.
However, heretofor, such calibration devices did not provide a closed environment for calibrating liquid metering devices, such that the liquid being metered is not exposed to the atmosphere. This is particularly desirable when calibrating a liquid metering device, such as an injector, used to additize fluids, for example, natural gas, propane or liquefied petroleum gas (LPG), with a liquid stenching agent, such as ethyl mercaptan, in that it is imperative that such a liquid stenching agent is not released to the atmosphere.